sha1_name.c

   1 #include "cache.h"
   2 #include "tag.h"
   3 #include "commit.h"
   4 #include "tree.h"
   5 #include "blob.h"
   6 #include "tree-walk.h"
   7 #include "refs.h"
   8 #include "remote.h"
   9
  10 static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
  11 {
  12         struct alternate_object_database *alt;
  13         char hex[40];
  14         int found = 0;
  15         static struct alternate_object_database *fakeent;
  16
  17         if (!fakeent) {
  18                 const char *objdir = get_object_directory();
  19                 int objdir_len = strlen(objdir);
  20                 int entlen = objdir_len + 43;
  21                 fakeent = xmalloc(sizeof(*fakeent) + entlen);
  22                 memcpy(fakeent->base, objdir, objdir_len);
  23                 fakeent->name = fakeent->base + objdir_len + 1;
  24                 fakeent->name[-1] = '/';
  25         }
  26         fakeent->next = alt_odb_list;
  27
  28         sprintf(hex, "%.2s", name);
  29         for (alt = fakeent; alt && found < 2; alt = alt->next) {
  30                 struct dirent *de;
  31                 DIR *dir;
  32                 sprintf(alt->name, "%.2s/", name);
  33                 dir = opendir(alt->base);
  34                 if (!dir)
  35                         continue;
  36                 while ((de = readdir(dir)) != NULL) {
  37                         if (strlen(de->d_name) != 38)
  38                                 continue;
  39                         if (memcmp(de->d_name, name + 2, len - 2))
  40                                 continue;
  41                         if (!found) {
  42                                 memcpy(hex + 2, de->d_name, 38);
  43                                 found++;
  44                         }
  45                         else if (memcmp(hex + 2, de->d_name, 38)) {
  46                                 found = 2;
  47                                 break;
  48                         }
  49                 }
  50                 closedir(dir);
  51         }
  52         if (found == 1)
  53                 return get_sha1_hex(hex, sha1) == 0;
  54         return found;
  55 }
  56
  57 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
  58 {
  59         do {
  60                 if (*a != *b)
  61                         return 0;
  62                 a++;
  63                 b++;
  64                 len -= 2;
  65         } while (len > 1);
  66         if (len)
  67                 if ((*a ^ *b) & 0xf0)
  68                         return 0;
  69         return 1;
  70 }
  71
  72 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
  73 {
  74         struct packed_git *p;
  75         const unsigned char *found_sha1 = NULL;
  76         int found = 0;
  77
  78         prepare_packed_git();
  79         for (p = packed_git; p && found < 2; p = p->next) {
  80                 uint32_t num, last;
  81                 uint32_t first = 0;
  82                 open_pack_index(p);
  83                 num = p->num_objects;
  84                 last = num;
  85                 while (first < last) {
  86                         uint32_t mid = (first + last) / 2;
  87                         const unsigned char *now;
  88                         int cmp;
  89
  90                         now = nth_packed_object_sha1(p, mid);
  91                         cmp = hashcmp(match, now);
  92                         if (!cmp) {
  93                                 first = mid;
  94                                 break;
  95                         }
  96                         if (cmp > 0) {
  97                                 first = mid+1;
  98                                 continue;
  99                         }
 100                         last = mid;
 101                 }
 102                 if (first < num) {
 103                         const unsigned char *now, *next;
 104                        now = nth_packed_object_sha1(p, first);
 105                         if (match_sha(len, match, now)) {
 106                                 next = nth_packed_object_sha1(p, first+1);
 107                                if (!next|| !match_sha(len, match, next)) {
 108                                         /* unique within this pack */
 109                                         if (!found) {
 110                                                 found_sha1 = now;
 111                                                 found++;
 112                                         }
 113                                         else if (hashcmp(found_sha1, now)) {
 114                                                 found = 2;
 115                                                 break;
 116                                         }
 117                                 }
 118                                 else {
 119                                         /* not even unique within this pack */
 120                                         found = 2;
 121                                         break;
 122                                 }
 123                         }
 124                 }
 125         }
 126         if (found == 1)
 127                 hashcpy(sha1, found_sha1);
 128         return found;
 129 }
 130
 131 #define SHORT_NAME_NOT_FOUND (-1)
 132 #define SHORT_NAME_AMBIGUOUS (-2)
 133
 134 static int find_unique_short_object(int len, char *canonical,
 135                                     unsigned char *res, unsigned char *sha1)
 136 {
 137         int has_unpacked, has_packed;
 138         unsigned char unpacked_sha1[20], packed_sha1[20];
 139
 140         prepare_alt_odb();
 141         has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
 142         has_packed = find_short_packed_object(len, res, packed_sha1);
 143         if (!has_unpacked && !has_packed)
 144                 return SHORT_NAME_NOT_FOUND;
 145         if (1 < has_unpacked || 1 < has_packed)
 146                 return SHORT_NAME_AMBIGUOUS;
 147         if (has_unpacked != has_packed) {
 148                 hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
 149                 return 0;
 150         }
 151         /* Both have unique ones -- do they match? */
 152         if (hashcmp(packed_sha1, unpacked_sha1))
 153                 return SHORT_NAME_AMBIGUOUS;
 154         hashcpy(sha1, packed_sha1);
 155         return 0;
 156 }
 157
 158 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 159                           int quietly)
 160 {
 161         int i, status;
 162         char canonical[40];
 163         unsigned char res[20];
 164
 165         if (len < MINIMUM_ABBREV || len > 40)
 166                 return -1;
 167         hashclr(res);
 168         memset(canonical, 'x', 40);
 169         for (i = 0; i < len ;i++) {
 170                 unsigned char c = name[i];
 171                 unsigned char val;
 172                 if (c >= '0' && c <= '9')
 173                         val = c - '0';
 174                 else if (c >= 'a' && c <= 'f')
 175                         val = c - 'a' + 10;
 176                 else if (c >= 'A' && c <='F') {
 177                         val = c - 'A' + 10;
 178                         c -= 'A' - 'a';
 179                 }
 180                 else
 181                         return -1;
 182                 canonical[i] = c;
 183                 if (!(i & 1))
 184                         val <<= 4;
 185                 res[i >> 1] |= val;
 186         }
 187
 188         status = find_unique_short_object(i, canonical, res, sha1);
 189         if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 190                 return error("short SHA1 %.*s is ambiguous.", len, canonical);
 191         return status;
 192 }
 193
 194 const char *find_unique_abbrev(const unsigned char *sha1, int len)
 195 {
 196         int status, exists;
 197         static char hex[41];
 198
 199         exists = has_sha1_file(sha1);
 200         memcpy(hex, sha1_to_hex(sha1), 40);
 201         if (len == 40 || !len)
 202                 return hex;
 203         while (len < 40) {
 204                 unsigned char sha1_ret[20];
 205                 status = get_short_sha1(hex, len, sha1_ret, 1);
 206                 if (exists
 207                     ? !status
 208                     : status == SHORT_NAME_NOT_FOUND) {
 209                         hex[len] = 0;
 210                         return hex;
 211                 }
 212                 len++;
 213         }
 214         return hex;
 215 }
 216
 217 static int ambiguous_path(const char *path, int len)
 218 {
 219         int slash = 1;
 220         int cnt;
 221
 222         for (cnt = 0; cnt < len; cnt++) {
 223                 switch (*path++) {
 224                 case '\0':
 225                         break;
 226                 case '/':
 227                         if (slash)
 228                                 break;
 229                         slash = 1;
 230                         continue;
 231                 case '.':
 232                         continue;
 233                 default:
 234                         slash = 0;
 235                         continue;
 236                 }
 237                 break;
 238         }
 239         return slash;
 240 }
 241
 242 static inline int tracked_suffix(const char *string, int len)
 243 {
 244         const char *suffix[] = { "@{upstream}", "@{u}" };
 245         int i;
 246
 247         for (i = 0; i < ARRAY_SIZE(suffix); i++) {
 248                 int suffix_len = strlen(suffix[i]);
 249                 if (len >= suffix_len && !memcmp(string + len - suffix_len,
 250                                         suffix[i], suffix_len))
 251                         return suffix_len;
 252         }
 253         return 0;
 254 }
 255
 256 /*
 257  * *string and *len will only be substituted, and *string returned (for
 258  * later free()ing) if the string passed in is of the form @{-<n>} or
 259  * of the form <branch>@{upstream}.
 260  */
 261 static char *substitute_branch_name(const char **string, int *len)
 262 {
 263         struct strbuf buf = STRBUF_INIT;
 264         int ret = interpret_branch_name(*string, &buf);
 265
 266         if (ret == *len) {
 267                 size_t size;
 268                 *string = strbuf_detach(&buf, &size);
 269                 *len = size;
 270                 return (char *)*string;
 271         }
 272
 273         ret = tracked_suffix(*string, *len);
 274         if (ret) {
 275                 char *ref = xstrndup(*string, *len - ret);
 276                 struct branch *tracking = branch_get(*ref ? ref : NULL);
 277
 278                 if (!tracking)
 279                         die ("No tracking branch found for '%s'", ref);
 280                 free(ref);
 281                 if (tracking->merge && tracking->merge[0]->dst) {
 282                         *string = xstrdup(tracking->merge[0]->dst);
 283                         *len = strlen(*string);
 284                         return (char *)*string;
 285                 }
 286         }
 287
 288         return NULL;
 289 }
 290
 291 int dwim_ref(const char *str, int len, unsigned char *sha1, char **ref)
 292 {
 293         char *last_branch = substitute_branch_name(&str, &len);
 294         const char **p, *r;
 295         int refs_found = 0;
 296
 297         *ref = NULL;
 298         for (p = ref_rev_parse_rules; *p; p++) {
 299                 char fullref[PATH_MAX];
 300                 unsigned char sha1_from_ref[20];
 301                 unsigned char *this_result;
 302                 int flag;
 303
 304                 this_result = refs_found ? sha1_from_ref : sha1;
 305                 mksnpath(fullref, sizeof(fullref), *p, len, str);
 306                 r = resolve_ref(fullref, this_result, 1, &flag);
 307                 if (r) {
 308                         if (!refs_found++)
 309                                 *ref = xstrdup(r);
 310                         if (!warn_ambiguous_refs)
 311                                 break;
 312                 } else if ((flag & REF_ISSYMREF) &&
 313                            (len != 4 || strcmp(str, "HEAD")))
 314                         warning("ignoring dangling symref %s.", fullref);
 315         }
 316         free(last_branch);
 317         return refs_found;
 318 }
 319
 320 int dwim_log(const char *str, int len, unsigned char *sha1, char **log)
 321 {
 322         char *last_branch = substitute_branch_name(&str, &len);
 323         const char **p;
 324         int logs_found = 0;
 325
 326         *log = NULL;
 327         for (p = ref_rev_parse_rules; *p; p++) {
 328                 struct stat st;
 329                 unsigned char hash[20];
 330                 char path[PATH_MAX];
 331                 const char *ref, *it;
 332
 333                 mksnpath(path, sizeof(path), *p, len, str);
 334                 ref = resolve_ref(path, hash, 1, NULL);
 335                 if (!ref)
 336                         continue;
 337                 if (!stat(git_path("logs/%s", path), &st) &&
 338                     S_ISREG(st.st_mode))
 339                         it = path;
 340                 else if (strcmp(ref, path) &&
 341                          !stat(git_path("logs/%s", ref), &st) &&
 342                          S_ISREG(st.st_mode))
 343                         it = ref;
 344                 else
 345                         continue;
 346                 if (!logs_found++) {
 347                         *log = xstrdup(it);
 348                         hashcpy(sha1, hash);
 349                 }
 350                 if (!warn_ambiguous_refs)
 351                         break;
 352         }
 353         free(last_branch);
 354         return logs_found;
 355 }
 356
 357 static int get_sha1_1(const char *name, int len, unsigned char *sha1);
 358
 359 static int get_sha1_basic(const char *str, int len, unsigned char *sha1)
 360 {
 361         static const char *warning = "warning: refname '%.*s' is ambiguous.\n";
 362         char *real_ref = NULL;
 363         int refs_found = 0;
 364         int at, reflog_len;
 365
 366         if (len == 40 && !get_sha1_hex(str, sha1))
 367                 return 0;
 368
 369         /* basic@{time or number or -number} format to query ref-log */
 370         reflog_len = at = 0;
 371         if (len && str[len-1] == '}') {
 372                 for (at = len-2; at >= 0; at--) {
 373                         if (str[at] == '@' && str[at+1] == '{') {
 374                                 if (!tracked_suffix(str + at, len - at)) {
 375                                         reflog_len = (len-1) - (at+2);
 376                                         len = at;
 377                                 }
 378                                 break;
 379                         }
 380                 }
 381         }
 382
 383         /* Accept only unambiguous ref paths. */
 384         if (len && ambiguous_path(str, len))
 385                 return -1;
 386
 387         if (!len && reflog_len) {
 388                 struct strbuf buf = STRBUF_INIT;
 389                 int ret;
 390                 /* try the @{-N} syntax for n-th checkout */
 391                 ret = interpret_branch_name(str+at, &buf);
 392                 if (ret > 0) {
 393                         /* substitute this branch name and restart */
 394                         return get_sha1_1(buf.buf, buf.len, sha1);
 395                 } else if (ret == 0) {
 396                         return -1;
 397                 }
 398                 /* allow "@{...}" to mean the current branch reflog */
 399                 refs_found = dwim_ref("HEAD", 4, sha1, &real_ref);
 400         } else if (reflog_len)
 401                 refs_found = dwim_log(str, len, sha1, &real_ref);
 402         else
 403                 refs_found = dwim_ref(str, len, sha1, &real_ref);
 404
 405         if (!refs_found)
 406                 return -1;
 407
 408         if (warn_ambiguous_refs && refs_found > 1)
 409                 fprintf(stderr, warning, len, str);
 410
 411         if (reflog_len) {
 412                 int nth, i;
 413                 unsigned long at_time;
 414                 unsigned long co_time;
 415                 int co_tz, co_cnt;
 416
 417                 /* Is it asking for N-th entry, or approxidate? */
 418                 for (i = nth = 0; 0 <= nth && i < reflog_len; i++) {
 419                         char ch = str[at+2+i];
 420                         if ('0' <= ch && ch <= '9')
 421                                 nth = nth * 10 + ch - '0';
 422                         else
 423                                 nth = -1;
 424                 }
 425                 if (100000000 <= nth) {
 426                         at_time = nth;
 427                         nth = -1;
 428                 } else if (0 <= nth)
 429                         at_time = 0;
 430                 else {
 431                         char *tmp = xstrndup(str + at + 2, reflog_len);
 432                         at_time = approxidate(tmp);
 433                         free(tmp);
 434                 }
 435                 if (read_ref_at(real_ref, at_time, nth, sha1, NULL,
 436                                 &co_time, &co_tz, &co_cnt)) {
 437                         if (at_time)
 438                                 fprintf(stderr,
 439                                         "warning: Log for '%.*s' only goes "
 440                                         "back to %s.\n", len, str,
 441                                         show_date(co_time, co_tz, DATE_RFC2822));
 442                         else
 443                                 fprintf(stderr,
 444                                         "warning: Log for '%.*s' only has "
 445                                         "%d entries.\n", len, str, co_cnt);
 446                 }
 447         }
 448
 449         free(real_ref);
 450         return 0;
 451 }
 452
 453 static int get_parent(const char *name, int len,
 454                       unsigned char *result, int idx)
 455 {
 456         unsigned char sha1[20];
 457         int ret = get_sha1_1(name, len, sha1);
 458         struct commit *commit;
 459         struct commit_list *p;
 460
 461         if (ret)
 462                 return ret;
 463         commit = lookup_commit_reference(sha1);
 464         if (!commit)
 465                 return -1;
 466         if (parse_commit(commit))
 467                 return -1;
 468         if (!idx) {
 469                 hashcpy(result, commit->object.sha1);
 470                 return 0;
 471         }
 472         p = commit->parents;
 473         while (p) {
 474                 if (!--idx) {
 475                         hashcpy(result, p->item->object.sha1);
 476                         return 0;
 477                 }
 478                 p = p->next;
 479         }
 480         return -1;
 481 }
 482
 483 static int get_nth_ancestor(const char *name, int len,
 484                             unsigned char *result, int generation)
 485 {
 486         unsigned char sha1[20];
 487         struct commit *commit;
 488         int ret;
 489
 490         ret = get_sha1_1(name, len, sha1);
 491         if (ret)
 492                 return ret;
 493         commit = lookup_commit_reference(sha1);
 494         if (!commit)
 495                 return -1;
 496
 497         while (generation--) {
 498                 if (parse_commit(commit) || !commit->parents)
 499                         return -1;
 500                 commit = commit->parents->item;
 501         }
 502         hashcpy(result, commit->object.sha1);
 503         return 0;
 504 }
 505
 506 struct object *peel_to_type(const char *name, int namelen,
 507                             struct object *o, enum object_type expected_type)
 508 {
 509         if (name && !namelen)
 510                 namelen = strlen(name);
 511         if (!o) {
 512                 unsigned char sha1[20];
 513                 if (get_sha1_1(name, namelen, sha1))
 514                         return NULL;
 515                 o = parse_object(sha1);
 516         }
 517         while (1) {
 518                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 519                         return NULL;
 520                 if (o->type == expected_type)
 521                         return o;
 522                 if (o->type == OBJ_TAG)
 523                         o = ((struct tag*) o)->tagged;
 524                 else if (o->type == OBJ_COMMIT)
 525                         o = &(((struct commit *) o)->tree->object);
 526                 else {
 527                         if (name)
 528                                 error("%.*s: expected %s type, but the object "
 529                                       "dereferences to %s type",
 530                                       namelen, name, typename(expected_type),
 531                                       typename(o->type));
 532                         return NULL;
 533                 }
 534         }
 535 }
 536
 537 static int peel_onion(const char *name, int len, unsigned char *sha1)
 538 {
 539         unsigned char outer[20];
 540         const char *sp;
 541         unsigned int expected_type = 0;
 542         struct object *o;
 543
 544         /*
 545          * "ref^{type}" dereferences ref repeatedly until you cannot
 546          * dereference anymore, or you get an object of given type,
 547          * whichever comes first.  "ref^{}" means just dereference
 548          * tags until you get a non-tag.  "ref^0" is a shorthand for
 549          * "ref^{commit}".  "commit^{tree}" could be used to find the
 550          * top-level tree of the given commit.
 551          */
 552         if (len < 4 || name[len-1] != '}')
 553                 return -1;
 554
 555         for (sp = name + len - 1; name <= sp; sp--) {
 556                 int ch = *sp;
 557                 if (ch == '{' && name < sp && sp[-1] == '^')
 558                         break;
 559         }
 560         if (sp <= name)
 561                 return -1;
 562
 563         sp++; /* beginning of type name, or closing brace for empty */
 564         if (!strncmp(commit_type, sp, 6) && sp[6] == '}')
 565                 expected_type = OBJ_COMMIT;
 566         else if (!strncmp(tree_type, sp, 4) && sp[4] == '}')
 567                 expected_type = OBJ_TREE;
 568         else if (!strncmp(blob_type, sp, 4) && sp[4] == '}')
 569                 expected_type = OBJ_BLOB;
 570         else if (sp[0] == '}')
 571                 expected_type = OBJ_NONE;
 572         else
 573                 return -1;
 574
 575         if (get_sha1_1(name, sp - name - 2, outer))
 576                 return -1;
 577
 578         o = parse_object(outer);
 579         if (!o)
 580                 return -1;
 581         if (!expected_type) {
 582                 o = deref_tag(o, name, sp - name - 2);
 583                 if (!o || (!o->parsed && !parse_object(o->sha1)))
 584                         return -1;
 585                 hashcpy(sha1, o->sha1);
 586         }
 587         else {
 588                 /*
 589                  * At this point, the syntax look correct, so
 590                  * if we do not get the needed object, we should
 591                  * barf.
 592                  */
 593                 o = peel_to_type(name, len, o, expected_type);
 594                 if (o) {
 595                         hashcpy(sha1, o->sha1);
 596                         return 0;
 597                 }
 598                 return -1;
 599         }
 600         return 0;
 601 }
 602
 603 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 604 {
 605         const char *cp;
 606
 607         for (cp = name + len - 1; name + 2 <= cp; cp--) {
 608                 char ch = *cp;
 609                 if (hexval(ch) & ~0377) {
 610                         /* We must be looking at g in "SOMETHING-g"
 611                          * for it to be describe output.
 612                          */
 613                         if (ch == 'g' && cp[-1] == '-') {
 614                                 cp++;
 615                                 len -= cp - name;
 616                                 return get_short_sha1(cp, len, sha1, 1);
 617                         }
 618                 }
 619         }
 620         return -1;
 621 }
 622
 623 static int get_sha1_1(const char *name, int len, unsigned char *sha1)
 624 {
 625         int ret, has_suffix;
 626         const char *cp;
 627
 628         /*
 629          * "name~3" is "name^^^", "name~" is "name~1", and "name^" is "name^1".
 630          */
 631         has_suffix = 0;
 632         for (cp = name + len - 1; name <= cp; cp--) {
 633                 int ch = *cp;
 634                 if ('0' <= ch && ch <= '9')
 635                         continue;
 636                 if (ch == '~' || ch == '^')
 637                         has_suffix = ch;
 638                 break;
 639         }
 640
 641         if (has_suffix) {
 642                 int num = 0;
 643                 int len1 = cp - name;
 644                 cp++;
 645                 while (cp < name + len)
 646                         num = num * 10 + *cp++ - '0';
 647                 if (!num && len1 == len - 1)
 648                         num = 1;
 649                 if (has_suffix == '^')
 650                         return get_parent(name, len1, sha1, num);
 651                 /* else if (has_suffix == '~') -- goes without saying */
 652                 return get_nth_ancestor(name, len1, sha1, num);
 653         }
 654
 655         ret = peel_onion(name, len, sha1);
 656         if (!ret)
 657                 return 0;
 658
 659         ret = get_sha1_basic(name, len, sha1);
 660         if (!ret)
 661                 return 0;
 662
 663         /* It could be describe output that is "SOMETHING-gXXXX" */
 664         ret = get_describe_name(name, len, sha1);
 665         if (!ret)
 666                 return 0;
 667
 668         return get_short_sha1(name, len, sha1, 0);
 669 }
 670
 671 static int handle_one_ref(const char *path,
 672                 const unsigned char *sha1, int flag, void *cb_data)
 673 {
 674         struct commit_list **list = cb_data;
 675         struct object *object = parse_object(sha1);
 676         if (!object)
 677                 return 0;
 678         if (object->type == OBJ_TAG) {
 679                 object = deref_tag(object, path, strlen(path));
 680                 if (!object)
 681                         return 0;
 682         }
 683         if (object->type != OBJ_COMMIT)
 684                 return 0;
 685         insert_by_date((struct commit *)object, list);
 686         return 0;
 687 }
 688
 689 /*
 690  * This interprets names like ':/Initial revision of "git"' by searching
 691  * through history and returning the first commit whose message starts
 692  * with the given string.
 693  *
 694  * For future extension, ':/!' is reserved. If you want to match a message
 695  * beginning with a '!', you have to repeat the exclamation mark.
 696  */
 697
 698 #define ONELINE_SEEN (1u<<20)
 699 static int get_sha1_oneline(const char *prefix, unsigned char *sha1)
 700 {
 701         struct commit_list *list = NULL, *backup = NULL, *l;
 702         int retval = -1;
 703         char *temp_commit_buffer = NULL;
 704
 705         if (prefix[0] == '!') {
 706                 if (prefix[1] != '!')
 707                         die ("Invalid search pattern: %s", prefix);
 708                 prefix++;
 709         }
 710         for_each_ref(handle_one_ref, &list);
 711         for (l = list; l; l = l->next)
 712                 commit_list_insert(l->item, &backup);
 713         while (list) {
 714                 char *p;
 715                 struct commit *commit;
 716                 enum object_type type;
 717                 unsigned long size;
 718
 719                 commit = pop_most_recent_commit(&list, ONELINE_SEEN);
 720                 if (!parse_object(commit->object.sha1))
 721                         continue;
 722                 free(temp_commit_buffer);
 723                 if (commit->buffer)
 724                         p = commit->buffer;
 725                 else {
 726                         p = read_sha1_file(commit->object.sha1, &type, &size);
 727                         if (!p)
 728                                 continue;
 729                         temp_commit_buffer = p;
 730                 }
 731                 if (!(p = strstr(p, "\n\n")))
 732                         continue;
 733                 if (!prefixcmp(p + 2, prefix)) {
 734                         hashcpy(sha1, commit->object.sha1);
 735                         retval = 0;
 736                         break;
 737                 }
 738         }
 739         free(temp_commit_buffer);
 740         free_commit_list(list);
 741         for (l = backup; l; l = l->next)
 742                 clear_commit_marks(l->item, ONELINE_SEEN);
 743         return retval;
 744 }
 745
 746 struct grab_nth_branch_switch_cbdata {
 747         long cnt, alloc;
 748         struct strbuf *buf;
 749 };
 750
 751 static int grab_nth_branch_switch(unsigned char *osha1, unsigned char *nsha1,
 752                                   const char *email, unsigned long timestamp, int tz,
 753                                   const char *message, void *cb_data)
 754 {
 755         struct grab_nth_branch_switch_cbdata *cb = cb_data;
 756         const char *match = NULL, *target = NULL;
 757         size_t len;
 758         int nth;
 759
 760         if (!prefixcmp(message, "checkout: moving from ")) {
 761                 match = message + strlen("checkout: moving from ");
 762                 target = strstr(match, " to ");
 763         }
 764
 765         if (!match || !target)
 766                 return 0;
 767
 768         len = target - match;
 769         nth = cb->cnt++ % cb->alloc;
 770         strbuf_reset(&cb->buf[nth]);
 771         strbuf_add(&cb->buf[nth], match, len);
 772         return 0;
 773 }
 774
 775 /*
 776  * This reads "@{-N}" syntax, finds the name of the Nth previous
 777  * branch we were on, and places the name of the branch in the given
 778  * buf and returns the number of characters parsed if successful.
 779  *
 780  * If the input is not of the accepted format, it returns a negative
 781  * number to signal an error.
 782  *
 783  * If the input was ok but there are not N branch switches in the
 784  * reflog, it returns 0.
 785  */
 786 int interpret_branch_name(const char *name, struct strbuf *buf)
 787 {
 788         long nth;
 789         int i, retval;
 790         struct grab_nth_branch_switch_cbdata cb;
 791         const char *brace;
 792         char *num_end;
 793
 794         if (name[0] != '@' || name[1] != '{' || name[2] != '-')
 795                 return -1;
 796         brace = strchr(name, '}');
 797         if (!brace)
 798                 return -1;
 799         nth = strtol(name+3, &num_end, 10);
 800         if (num_end != brace)
 801                 return -1;
 802         if (nth <= 0)
 803                 return -1;
 804         cb.alloc = nth;
 805         cb.buf = xmalloc(nth * sizeof(struct strbuf));
 806         for (i = 0; i < nth; i++)
 807                 strbuf_init(&cb.buf[i], 20);
 808         cb.cnt = 0;
 809         retval = 0;
 810         for_each_recent_reflog_ent("HEAD", grab_nth_branch_switch, 40960, &cb);
 811         if (cb.cnt < nth) {
 812                 cb.cnt = 0;
 813                 for_each_reflog_ent("HEAD", grab_nth_branch_switch, &cb);
 814         }
 815         if (cb.cnt < nth)
 816                 goto release_return;
 817         i = cb.cnt % nth;
 818         strbuf_reset(buf);
 819         strbuf_add(buf, cb.buf[i].buf, cb.buf[i].len);
 820         retval = brace-name+1;
 821
 822 release_return:
 823         for (i = 0; i < nth; i++)
 824                 strbuf_release(&cb.buf[i]);
 825         free(cb.buf);
 826
 827         return retval;
 828 }
 829
 830 /*
 831  * This is like "get_sha1_basic()", except it allows "sha1 expressions",
 832  * notably "xyz^" for "parent of xyz"
 833  */
 834 int get_sha1(const char *name, unsigned char *sha1)
 835 {
 836         unsigned unused;
 837         return get_sha1_with_mode(name, sha1, &unused);
 838 }
 839
 840 int get_sha1_with_mode(const char *name, unsigned char *sha1, unsigned *mode)
 841 {
 842         int ret, bracket_depth;
 843         int namelen = strlen(name);
 844         const char *cp;
 845
 846         *mode = S_IFINVALID;
 847         ret = get_sha1_1(name, namelen, sha1);
 848         if (!ret)
 849                 return ret;
 850         /* sha1:path --> object name of path in ent sha1
 851          * :path -> object name of path in index
 852          * :[0-3]:path -> object name of path in index at stage
 853          */
 854         if (name[0] == ':') {
 855                 int stage = 0;
 856                 struct cache_entry *ce;
 857                 int pos;
 858                 if (namelen > 2 && name[1] == '/')
 859                         return get_sha1_oneline(name + 2, sha1);
 860                 if (namelen < 3 ||
 861                     name[2] != ':' ||
 862                     name[1] < '0' || '3' < name[1])
 863                         cp = name + 1;
 864                 else {
 865                         stage = name[1] - '0';
 866                         cp = name + 3;
 867                 }
 868                 namelen = namelen - (cp - name);
 869                 if (!active_cache)
 870                         read_cache();
 871                 pos = cache_name_pos(cp, namelen);
 872                 if (pos < 0)
 873                         pos = -pos - 1;
 874                 while (pos < active_nr) {
 875                         ce = active_cache[pos];
 876                         if (ce_namelen(ce) != namelen ||
 877                             memcmp(ce->name, cp, namelen))
 878                                 break;
 879                         if (ce_stage(ce) == stage) {
 880                                 hashcpy(sha1, ce->sha1);
 881                                 *mode = ce->ce_mode;
 882                                 return 0;
 883                         }
 884                         pos++;
 885                 }
 886                 return -1;
 887         }
 888         for (cp = name, bracket_depth = 0; *cp; cp++) {
 889                 if (*cp == '{')
 890                         bracket_depth++;
 891                 else if (bracket_depth && *cp == '}')
 892                         bracket_depth--;
 893                 else if (!bracket_depth && *cp == ':')
 894                         break;
 895         }
 896         if (*cp == ':') {
 897                 unsigned char tree_sha1[20];
 898                 if (!get_sha1_1(name, cp-name, tree_sha1))
 899                         return get_tree_entry(tree_sha1, cp+1, sha1,
 900                                               mode);
 901         }
 902         return ret;
 903 }